The present invention relates to a secondary charged particle analyzing apparatus, in which secondary charged particles (secondary ions and secondary electrons) generated from an object to be examined by irradiating it with primary charged particles (primary ions and primary electrons) are focused and the secondary charged particles are analyzed.
As secondary charged particle analyzing apparatuses there are known secondary ion mass analyzing apparatuses and scanning electron microscopes.
For example, in the case where constituent elements of a semiconductor device such as an LSI, etc. are analyzed by means of a secondary ion mass analyzing apparatus, constituent elements in an irradiated domain are sputtered by irradiating the object to be examined with a primary ion beam and the mass of the secondary ions thus obtained is analyzed. However, owing to an increase in the packing density in semiconductor devices to an ultra high density by recent LSI techniques, sizes of constituent members, wiring widths in LSIs, etc., smaller than 1 .mu.m have been realized. In addition, the concentration of impurities implanted in a semiconductor device varies by a factor greater than 6 orders of magnitude, depending on the place. In order to analyze such a fine domain with a high precision, it is necessary to narrow the domain irradiated with the primary ion beam. However, because of the space charge effect it is difficult to narrow the primary ion beam and the diameter thereof can be hardly reduced to several micrometers. Consequently, according to the prior art techniques, in the case where elements are to be analyzed for such an ultra fine domain, the selected area method is adopted, by which a domain, whose diameter is several micrometers, is irradiated with the primary ion beam and a secondary ion beam emitted by this domain is focused through a lens system (hereinbelow called a secondary charged particle extracting section) and among obtained images only images of the ultra fine domain to be examined are taken out through a slit, etc., and injected in a mass analyzing system. However, according to the simple prior art selected area method, e.g. when the mass difference is as small as for 1/4000 such as .sup.31 P and .sup.30 Si.sup.1 H, the mass analysis itself is difficult and it is necessary to improve the property of the beam projected to the mass analyzing system.